Classics
in the History of Psychology

[Review of] The Origin of Species by
Means of Natural Selection

by Asa Gray (1860)

First published in American Journal of Science and Arts,
March, 1860
Reprinted in Gray, Asa. (1876). Darwiniana:
Essays and Reviews Pertaining to Darwinism. New York.

Posted
June 2004

This book is already exciting much attention. Two American editions
are announced, through which it will become familiar to many of our readers,
before these pages are issued. An abstract of the argument -- for "the
whole volume is one long argument," as the author states -- is unnecessary
in such a case; and it would be difficult to give by detached extracts. For the
volume itself is an abstract, a prodromus of a detailed work upon which the
author has been laboring for twenty years, and which "will take two or three
more years to complete." It is exceedingly compact; and although useful
summaries are appended to the several chapters, and a general recapitulation
contains the essence of the whole, yet much of the aroma escapes in the treble
distillation, or is so concentrated that the flavor is lost to the general or
even to the scientific reader. The volume itself -- the proof-spirit -- is just
condensed enough for its purpose. It will be far more widely read, and perhaps
will make deeper impression, than the elaborate work might have done, with all
its full details of the facts upon which the author's sweeping conclusions have
been grounded. At least it is a more readable book: but all the facts that can
be mustered in favor of the theory are still likely to be needed.

Who, upon a single perusal, shall pass judgment upon a work like
this, to which twenty of the best years of the life of a most able naturalist
have been devoted? And who among those naturalists who hold a position that
entitles them to pronounce summarily upon the subject, can be expected to
divest himself for the nonce of the influence of received and favorite systems?
In fact, the controversy now opened is not likely to be settled in an off-hand
way, nor is it desirable that it should be. A spirited conflict among opinions
of every grade must ensue, which -- to borrow an illustration from the doctrine
of the book before us -- may be likened to the conflict in Nature among races
in the struggle for life, which Mr. Darwin describes; through which the views
most favored by facts will be developed and tested by "Natural
Selection," the weaker ones be destroyed in the process, and the strongest
in the long-run alone survive.

The duty of reviewing this volume in the American Journal of Science
would naturally devolve upon the principal editor,' whose wide observation and
profound knowledge of various departments of natural history, as well as of
geology, particularly qualify him for the task. But he has been obliged to lay
aside his pen, and to seek in distant lands the entire repose from scientific
labor so essential to the restoration of his health -- a consummation devoutly
to be wished, and confidently to be expected. Interested as Mr. Dana would be
in this volume, he could not be expected to accept this doctrine.

Views so idealistic as those upon which his "Thoughts upon
Species" [I-2] are grounded, will not harmonize readily with a doctrine so
thoroughly naturalistic as that of Mr. Darwin. Though it is just possible that
one who regards the kinds of elementary matter, such as oxygen and hydrogen,
and the definite compounds of these elementary matters, and their compounds
again, in the mineral kingdom, as constituting species, in the same sense,
fundamentally, as that of animal and vegetable species, might admit an
evolution of one species from another in the latter as well as the former case.

Between the doctrines of this volume and those of the other great
naturalist whose name adorns the title-page of this journal, the widest
divergence appears. It is interesting to contrast the two, and, indeed, is
necessary to our purpose; for this contrast brings out most prominently, and
sets in strongest light and shade, the main features of the theory of the
origination of species by means of Natural Selection.

The ordinary and generally-received view assumes the independent,
specific creation of each kind of plant and animal in a primitive stock, which
reproduces its like from generation to generation, and so continues the
species. Taking the idea of species from this perennial succession of
essentially similar individuals, the chain is logically traceable back to a
local origin in a single stock, a single pair, or a single individual, from
which all the individuals composing the species have proceeded by natural generation.
Although the similarity of progeny to parent is fundamental in the conception
of species, yet the likeness is by no means absolute; all species vary more or
less, and some vary remarkably -- partly from the influence of altered
circumstances, and partly (and more really) from unknown constitutional causes
which altered conditions favor rather than originate. But these variations are
supposed to be mere oscillations from a normal state, and in Nature to be
limited if not transitory; so that the primordial differences between species
and species at their beginning have not been effaced, nor largely obscured, by
blending through variation. Consequently, whenever two reputed species are
found to blend in Nature through a series of intermediate forms, community of
origin is inferred, and all the forms, however diverse, are held to belong to
one species. Moreover, since bisexuality is the rule in Nature (which is
practically carried out, in the long-run, far more generally than has been
suspected), and the heritable qualities of two distinct individuals are mingled
in the offspring, it is supposed that the general sterility of hybrid progeny
interposes an effectual barrier against the blending of the original species by
crossing.

From this generally-accepted view the well-known theory of Agassiz and the recent one of Darwin diverge in
exactly opposite directions.

That of Agassiz differs fundamentally from the ordinary view only in
this, that it discards the idea of a common descent as the real bond of union among
the individuals of a species, and also the idea of a local origin -- supposing,
instead, that each species originated simultaneously, generally speaking, over
the whole geographical area it now occupies or has occupied, and in perhaps as
many individuals as it numbered at any subsequent period.

Mr. Darwin, on the other hand, holds the orthodox view of the
descent of all the individuals of a species not only from a local birthplace,
but from a single ancestor or pair; and that each species has extended and
established itself, through natural agencies, wherever it could; so that the
actual geographical distribution of any species is by no means a primordial
arrangement, but a natural result. He goes farther, and this volume is a
protracted argument intended to prove that the species we recognize have not
been independently created, as such, but have descended, like varieties, from
other species. Varieties, on this view, are incipient or possible species:
species are varieties of a larger growth and a wider and earlier divergence
from the parent stock; the difference is one of degree, not of kind.

The ordinary view -- rendering unto Caesar the things that are
Caesar's -- looks to natural agencies for the actual distribution and
perpetuation of species, to a supernatural for their origin.

The theory of Agassiz regards the origin of species and their present general
distribution over the world as equally primordial, equally supernatural; that
of Darwin, as equally derivative, equally natural.

The theory of Agassiz, referring as it does the phenomena both of
origin and distribution directly to the Divine will -- thus removing the latter
with the former out of the domain of inductive science (in which efficient
cause is not the first, but the last word) -- may be said to be theistic to
excess. The contrasted theory is not open to this objection. Studying the facts
and phenomena in reference to proximate causes, and endeavoring to trace back
the series of cause and effect as far as possible, Darwin's aim and processes
are strictly scientific, and his endeavor, whether successful or futile, must
be regarded as a legitimate attempt to extend the domain of natural or physical
science. For, though it well may be that "organic forms have no physical
or secondary cause," yet this can be proved only indirectly, by the
failure of every attempt to refer the phenomena in question to causal laws.
But, however originated, and whatever be thought of Mr. Darwin's arduous
undertaking in this respect, it is certain that plants and animals are subject
from their birth to physical influences, to which they have to accommodate
themselves as they can. How literally they are "born to trouble," and
how incessant and severe the struggle for life generally is, the present volume
graphically describes. Few will deny that such influences must have gravely
affected the range and the association of individuals and species on the
earth's surface. Mr. Darwin thinks that, acting upon an inherent predisposition
to vary, they have sufficed even to modify the species themselves and produce
the present diversity. Mr. Agassiz believes that they have not even affected
the geographical range and the actual association of species, still less their
forms; but that every adaptation of species to climate, and of species to
species, is as aboriginal, and therefore as inexplicable, as are the organic
forms themselves.

Who shall decide between such extreme views so ably maintained on
either hand, and say how much of truth there may be in each? The present
reviewer has not the presumption to undertake such a task. Having no
prepossession in favor of naturalistic theories, but struck with the eminent
ability of Mr. Darwin's work, and charmed with its fairness, our humbler duty
will be performed if, laying aside prejudice as much as we can, we shall
succeed in giving a fair account of its method and argument, offering by the
way a few suggestions, such as might occur to any naturalist of an inquiring
mind. An editorial character for this article must in justice be disclaimed.
The plural pronoun is employed not to give editorial weight, but to avoid even
the appearance of egotism, and also the circumlocution which attends a rigorous
adherence to the impersonal style.

We have contrasted these two extremely divergent theories, in their
broad statements. It must not be inferred that they have no points nor ultimate
results in common.

In the first place, they practically agree in upsetting, each in its
own way, the generally-received definition of species, and in sweeping away the
ground of their objective existence in Nature. The orthodox conception of
species is that of lineal descent: all the descendants of a common parent, and
no other, constitute a species; they have a certain identity because of their
descent, by which they are supposed to be recognizable. So naturalists had a
distinct idea of what they meant by the term species, and a practical rule,
which was hardly the less useful because difficult to apply in many cases, and
because its application was indirect: that is, the community of origin had to
be inferred from the likeness; such degree of similarity, and such only, being
held to be con-specific as could be shown or reasonably inferred to be
compatible with a common origin. And the usual concurrence of the whole body of
naturalists (having the same data before them) as to what forms are species
attests the value of the rule, and also indicates some real foundation for it
in Nature. But if species were created in numberless individuals over broad
spaces of territory, these individuals are connected only in idea, and species
differ from varieties on the one hand, and from genera, tribes, etc., on the
other, only in degree; and no obvious natural reason remains for fixing upon
this or that degree as specific, at least no natural standard, by which the
opinions of different naturalists may be correlated. Species upon this view are
enduring, but subjective and ideal. Any three or more of the human races, for
example, are species or not species, according to the bent of the naturalist's
mind. Darwin's theory brings us the other way to the same result. In his view,
not only all the individuals of a species are descendants of a common parent,
but of all the related species also. Affinity, relationship, all the terms
which naturalists use figuratively to express an underived, unexplained
resemblance among species, have a literal meaning upon Darwin's system, which
they little suspected, namely, that of inheritance. Varieties are the latest
offshoots of the genealogical tree in "an unlineal" order; species,
those of an earlier date, but of no definite distinction; genera, more ancient
species, and so on. The human races, upon this view, likewise may or may not be
species according to the notions of each naturalist as to what differences are
specific; but, if not species already, those races that last long enough are
sure to become so. It is only a question of time.

How well the simile of a genealogical tree illustrates the main
ideas of Darwin's theory the following extract from the summary of the fourth
chapter shows:

"It is a truly wonderful fact -- the wonder of which we are apt
to overlook from familiarity -- that all animals and all plants throughout all
time and space should be related to each other in group subordinate to group,
in the manner which we everywhere behold -- namely, varieties of the same
species most closely related together, species of the same genus less closely
and unequally related together, forming sections and sub-genera, species of
distinct genera much less closely related, and genera related in different
degrees, forming sub-families, families, orders, sub-classes, and classes. The
several subordinate groups in any class cannot be ranked in a single file, but
seem rather to be clustered round points, and these round other points, and so
on in almost endless cycles. On the view that each species has been
independently created, I can see no explanation of this great fact in the
classification of all organic beings; but, to the best of my judgment, it is explained
through inheritance and the complex action of natural selection, entailing
extinction and divergence of character, as we have seen illustrated in the
diagram.

"The affinities of all the beings of the same class have sometimes
been represented by a great tree. I believe this simile largely speaks the
truth. The green and budding twigs may represent existing species; and those
produced during each former year may represent the long succession of extinct
species. At each period of growth all the growing twigs have tried to branch
out on all sides, and overtop and kill the surrounding twigs and branches, in
the same manner as species and groups of species have tried to overmaster other
species in the great battle for life. The limbs divided into great branches,
and these into lesser and lesser branches, were themselves once, when the tree
was small, budding twigs; and this connection of the former and present buds by
ramifying branches may well represent the classification of all extinct and
living species in groups subordinate to groups. Of the many twigs which
flourished when the tree was a mere bush, only two or three, now grown into
great branches, yet survive and bear all the other branches; so with the
species which lived during long-past geological periods, very few now have
living and modified descendants. From the first growth of the tree, many a limb
and branch has decayed and dropped off; and these lost branches of various
sizes may represent those whole orders, families, and genera, which have now no
living representatives, and which are known to us only from having been found
in a fossil state. As we here and there see a thin, straggling branch springing
from a fork low down in a tree, and which by some chance has been favored and
is still alive on its summit, so we occasionally see an animal like the
Ornithorhynchus or Lepidosiren, which in some small degree connects by its
affinities two large branches of life, and which has apparently been saved from
fatal competition by having inhabited a protected station. As buds give rise by
growth to fresh buds, and these, if vigorous, branch out and overtop on all
sides many a feebler branch, so by generation I believe it has been with the
great Tree of Life, which fills with its dead and broken branches the crust of
the earth, and covers the surface with its ever-branching and beautiful
ramification."

It may also be noted that
there is a significant correspondence between the rival theories as to the main
facts employed. Apparently every capital fact in the one view is a capital fact
in the other. The difference is in the interpretation. To run the parallel
ready made to our hands: [I-4]

"The simultaneous
existence of the most diversified types under identical circumstances ... the
repetition of similar types under the most diversified circumstances ... the
unity of plan in otherwise highly-diversified types of animals ... the
correspondence, now generally known as special homologies, in the details of
structure otherwise entirely disconnected, down to the most minute
peculiarities ... the various degrees and different kinds of relationship among
animals which (apparently) can have no genealogical connection ... the
simultaneous existence in the earliest geological periods, ... of
representatives of all the great types of the animal kingdom ... the gradation
based upon complications of structure which may be traced among animals built
upon the same plan; the distribution of some types over the most extensive
range of surface of the globe, while others are limited to particular
geographical areas ... the identity of structures of these types,
notwithstanding their wide geographical distribution ... the community of
structure in certain respects of animals otherwise entirely different, but
living within the same geographical area ... the connection by series of
special structures observed in animals widely scattered over the surface of the
globe ... the definite relations in which animals stand to the surrounding
world, ... the relations in which individuals of the same species stand to one
another ... the limitation of the range of changes which animals undergo during
their growth ... the return to a definite norm of animals which multiply in
various ways ... the order of succession of the different types of animals and
plants characteristic of the different geological epochs, ... the localization
of some types of animals upon the same points of the surface of the globe
during several successive geological periods ... the parallelism between the
order of succession of animals and plants in geological times, and the
gradation among their living representatives ... the parallelism between the
order of succession of animals in geological times and the changes their living
representatives undergo during their embryological growth, [I-5] ... the
combination in many extinct types of characters which in later ages appear
disconnected in different types, ... the parallelism between the gradation
among animals and the changes they undergo during their growth, ... the
relations existing between these different series and the geographical
distribution of animals, ... the connection of all the known features of Nature
into one system -- "

In a word, the whole
relations of animals, etc., to surrounding Nature and to each other, are
regarded under the one view as ultimate facts, or in the ultimate aspect, and
interpreted theologically; under the other as complex facts, to be analyzed and
interpreted scientifically. The one naturalist, perhaps too largely assuming
the scientifically unexplained to be inexplicable, views the phenomena only in
their supposed relation to the Divine mind. The other, naturally expecting many
of these phenomena to be resolvable under investigation, views them in their relations
to one another, and endeavors to explain them as far as he can (and perhaps
farther) through natural causes.

But does the one really exclude the other? Does the investigation of
physical causes stand opposed to the theological view and the study of the
harmonies between mind and Nature? More than this, is it not most presumable
that an intellectual conception realized in Nature would be realized through
natural agencies? Mr. Agassiz answers these questions affirmatively when he
declares that "the task of science is to investigate what has been done,
to inquire if possible how it has been done, rather than to ask what is
possible for the Deity, since we can know that only by what actually
exists;" and also when he extends the argument for the intervention in
Nature of a creative mind to its legitimate application in the inorganic world;
which, he remarks, "considered in the same light, would not fail also to
exhibit unexpected evidence of thought, in the character of the laws regulating
the chemical combinations, the action of physical forces, etc., etc."
[I-6] Mr. Agassiz, however, pronounces that "the connection between the
facts is only intellectual" -- an opinion which the analogy of the
inorganic world, just referred to, does not confirm, for there a material
connection between the facts is justly held to be consistent with an
intellectual -- and which the most analogous cases we can think of in the
organic world do not favor; for there is a material connection between the
grub, the pupa, and the butterfly, between the tadpole and the frog, or, still
better, between those distinct animals which succeed each other in alternate
and very dissimilar generations. So that mere analogy might rather suggest a
natural connection than the contrary; and the contrary cannot be demonstrated
until the possibilities of Nature under the Deity are fathomed.

But, the intellectual connection being undoubted, Mr. Agassiz
properly refers the whole to "the agency of Intellect as its first
cause." In doing so, however, he is not supposed to be offering a
scientific explanation of the phenomena. Evidently he is considering only the
ultimate why, not the proximate why or how.

Now the latter is just what Mr. Darwin is considering. He conceives
of a physical connection between allied species; but we suppose he does not
deny their intellectual connection, as related to a supreme intelligence.
Certainly we see no reason why he should, and many reasons why he should not,
Indeed, as we contemplate the actual direction of investigation and speculation
in the physical and natural sciences, we dimly apprehend a probable synthesis
of these divergent theories, and in it the ground for a strong stand against
mere naturalism. Even if the doctrine of the origin of species through natural
selection should prevail in our day, we shall not despair; being confident that
the genius of an Agassiz will be found equal to the work of constructing, upon
the mental and material foundations combined, a theory of Nature as theistic
and as scientific as that which he has so eloquently expounded.

To conceive the possibility of "the descent of species from
species by insensibly fine gradations" during a long course of time, and
to demonstrate its compatibility with a strictly theistic view of the universe,
is one thing; to substantiate the theory itself or show its likelihood is quite
another thing. This brings us to consider what Darwin's theory actually is, and
how he supports it.

That the existing kinds of animals and plants, or many of them, may
be derived from other and earlier kinds, in the lapse of time, is by no means a
novel proposition. Not to speak of ancient speculations of the sort, it is the
well-known Lamarckian theory. The first difficulty which such theories meet
with is that in the present age, with all its own and its inherited
prejudgments, the whole burden of proof is naturally, and indeed properly, laid
upon the shoulders of the propounders; and thus far the burden has been more
than they could bear. From the very nature of the case, substantive proof of
specific creation is not attainable; but that of derivation or transmutation of
species may be. He who affirms the latter view is bound to do one or both of
two things: 1. Either to assign real and adequate causes, the natural or
necessary result of which must be to produce the present diversity of species
and their actual relations; or, 2. To show the general conformity of the whole
body of facts to such assumption, and also to adduce instances explicable by it
and inexplicable by the received view, so perhaps winning our assent to the
doctrine, through its competency to harmonize all the facts, even though the
cause of the assumed variation remain as occult as that of the transformation
of tadpoles into frogs, or that of Coryne into Sarzia.

The first line of proof, successfully carried out, would establish
derivation as a true physical theory; the second, as a sufficient hypothesis.

Lamarck mainly undertook the first line, in a theory which has been
so assailed by ridicule that it rarely receives the credit for ability to which
in its day it was entitled, But he assigned partly unreal, partly insufficient
causes; and the attempt to account for a progressive change in species through
the direct influence of physical agencies, and through the appetencies and
habits of animals reacting upon their structure, thus causing the production
and the successive modification of organs, is a conceded and total failure. The
shadowy author of the "Vestiges of the Natural History of Creation"
can hardly be said to have undertaken either line, in a scientific way. He
would explain the whole progressive evolution of Nature by virtue of an
inherent tendency to development, thus giving us an idea or a word in place of
a natural cause, a restatement of the proposition instead of an explanation.
Mr. Darwin attempts both lines of proof, and in a strictly scientific spirit;
but the stress falls mainly upon the first, for, as he does assign real causes,
he is bound to prove their adequacy.

It should be kept in mind that, while all direct proof of
independent origination is attainable from the nature of the case, the
overthrow of particular schemes of derivation has not established the opposite
proposition. The futility of each hypothesis thus far proposed to account for derivation
may be made apparent, or unanswerable objections may be urged against it; and
each victory of the kind may render derivation more improbable, and therefore
specific creation more probable, without settling the question either way. New
facts, or new arguments and a new mode of viewing the question, may some day
change the whole aspect of the case. It is with the latter that Mr. Darwin now
reopens the discussion.

Having conceived the idea that varieties are incipient species, he
is led to study variation in the field where it shows itself most strikingly,
and affords the greatest facilities to investigation. Thoughtful naturalists
have had increasing grounds to suspect that a reexamination of the question of
species in zoology and botany, commencing with those races which man knows most
about, viz., the domesticated and cultivated races, would be likely somewhat to
modify the received idea of the entire fixity of species. This field, rich with
various but unsystematized stores of knowledge accumulated by cultivators and
breeders, has been generally neglected by naturalists, because these races are
not in a state of nature; whereas they deserve particular attention on this
very account, as experiments, or the materials for experiments, ready to our
hand. In domestication we vary some of the natural conditions of a species, and
thus learn experimentally what changes are within the reach of varying
conditions in Nature. We separate and protect a favorite race against its foes
or its competitors, and thus learn what it might become if Nature ever afforded
it equal opportunities. Even when, to subserve human uses, we modify a
domesticated race to the detriment of its native vigor, or to the extent of
practical monstrosity, although we secure forms which would not be originated
and could not be perpetuated in free Nature, yet we attain wider and juster
views of the possible degree of variation. We perceive that some species are
more variable than others, but that no species subjected to the experiment
persistently refuses to vary; and that, when it has once begun to vary, its
varieties are not the less but the more subject to variation. "No case is
on record of a variable being ceasing to be variable under cultivation."
It is fair to conclude, from the observation of plants and animals in a wild as
well as domesticated state, that the tendency to vary is general, and even
universal. Mr. Darwin does "not believe that variability is an inherent
and necessary contingency, under all circumstances, with all organic beings, as
some authors have thought." No one supposes variation could occur under
all circumstances; but the facts on the whole imply a universal tendency, ready
to be manifested under favorable circumstances. In reply to the assumption that
man has chosen for domestication animals and plants having an extraordinary
inherent tendency to vary, and likewise to withstand diverse climates, it is
asked:

"How could a savage
possibly know, when he first tamed an animal, whether it would vary in
succeeding generations and whether it would endure other climates? Has the
little variability of the ass or Guinea-fowl, or the small power of endurance
of warmth by the reindeer, or of cold by the common camel, prevented their
domestication? I cannot doubt that if other animals and plants, equal in number
to our domesticated productions, and belonging to equally diverse classes and
countries, were taken from a state of nature, and could be made to breed for an
equal number of generations under domestication, they would vary on an average
as largely as the parent species of our existing domesticated productions have
varied."

As to amount of variation,
there is the common remark of naturalists that the varieties of domesticated
plants or animals often differ more widely than do the individuals of distinct
species in a wild state: and even in Nature the individuals of some species are
known to vary to a degree sensibly wider than that which separates related
species. In his instructive section on the breeds of the domestic pigeon, our
author remarks that "at least a score of pigeons might be chosen which if
shown to an ornithologist, and he were told that they were wild birds, would
certainly be ranked by him as well-defined species. Moreover, I do not believe
that any ornithologist would place the English carrier, the short-faced
tumbler, the runt, the barb, pouter, and fantail, in the same genus; more
especially as in each of these breeds several truly-inherited sub-breeds, or
species, as he might have called them, could be shown him." That this is
not a case like that of dogs, in which probably the blood of more than one
species is mingled, Mr. Darwin proceeds to show, adducing cogent reasons for
the common opinion that all have descended from the wild rock-pigeon. Then follow
some suggestive remarks:

"I have discussed the
probable origin of domestic pigeons at some, yet quite insufficient, length;
because when I first kept pigeons and watched the several kinds, knowing well
how true they bred, I felt fully as much difficulty in believing that they
could ever have descended from a common parent as any naturalist could in
coming to a similar conclusion in regard to many species of finches, or other
large groups of birds, in Nature. One circumstance has struck me much; namely,
that all the breeders of the various domestic animals and the cultivators of
plants, with whom I have ever conversed, or whose treatises I have read, are
firmly convinced that the several breeds to which each has attended are
descended from so many aboriginally distinct species. Ask, as I have asked, a
celebrated raiser of Hereford cattle, whether his cattle might not have descended from
long-horns, and he will laugh you to scorn. I have never met a pigeon, or
poultry, or duck, or rabbit fancier, who was not fully convinced that each main
breed was descended from a distinct species. Van Mons, in his treatise on pears
and apples, shows how utterly he disbelieves that the several sorts, for
instance a Ribston-pippin or Codlin-apple, could ever have proceeded from the
seeds of the same tree. Innumerable other examples could be given. The
explanation, I think, is simple: from long-continued study they arc strongly
impressed with the differences between the several races; and though they well
know that each race varies slightly, for they win their prizes by selecting
such slight differences, yet they ignore all general arguments, and refuse to
sum up in their minds slight differences accumulated during many successive
generations. May not those naturalists who, knowing far less of the laws of
inheritance than does the breeder, and knowing no more than he does of the
intermediate links in the long lines of descent, yet admit that many of our
domestic races have descended from the same parents -- may they not learn a
lesson of caution, when they deride the idea of species in a state of nature
being lineal descendants of other species?"

The actual causes of
variation are unknown. Mr. Darwin favors the opinion of the late Mr. Knight,
the great philosopher of horticulture, that variability tinder domestication is
somehow connected with excess of food. He regards the unknown cause as acting
chiefly upon the reproductive system of the parents, which system, judging from
the effect of confinement or cultivation upon its functions, he concludes to be
more susceptible than any other to the action of changed conditions of life.
The tendency to vary certainly appears to be much stronger under domestication
than in free Nature. But we are not sure that the greater variableness of cultivated
races is not mainly owing to the far greater opportunities for manifestation
and accumulation -- a view seemingly all the more favorable to Mr. Darwin's
theory. The actual amount of certain changes, such as size or abundance of
fruit, size of udder, stands of course in obvious relation to supply of
food.Really, we no more know the
reason why the progeny occasionally deviates from the parent than we do why it
usually resembles it. Though the laws and conditions governing variation are
known to a certain extent, those governing inheritance are apparently
inscrutable. "Perhaps," Darwin remarks, "the correct way of
viewing the whole subject would be, to look at the inheritance of every
character whatever as the rule, and non-inheritance as the anomaly." This,
from general and obvious considerations, we have long been accustomed to do.
Now, as exceptional instances are expected to be capable of explanation, while
ultimate laws are not, it is quite possible that variation may be accounted
for, while the great primary law of inheritance remains a mysterious fact.

The common proposition is, that species reproduce their like; this
is a sort of general inference, only a degree closer to fact than the statement
that genera reproduce their like. The true proposition, the fact incapable of
further analysis, is, that individuals reproduce their like -- that
characteristics are inheritable. So varieties, or deviations, once originated,
are perpetuable, like species. Not so likely to be perpetuated, at the outset;
for the new form tends to resemble a grandparent and a long line of similar
ancestors, as well as to resemble its immediate progenitors. Two forces which
coincide in the ordinary case, where the offspring resembles its parent, act in
different directions when it does not and it is uncertain which will prevail.
If the remoter but very potent ancestral influence predominates, the variation
disappears with the life of the individual. If that of the immediate parent --
feebler no doubt, but closer -- the variety survives in the offspring; whose
progeny now has a redoubled tendency to produce its own like; whose progeny
again is almost sure to produce its like, since it is much the same whether it
takes after its mother or its grandmother.

In this way races arise, which under favorable conditions may be as
hereditary as species. In following these indications, watching opportunities,
and breeding only from those individuals which vary most in a desirable
direction, man leads the course of variation as he leads a streamlet --
apparently at will, but never against the force of gravitation -- to a long
distance from its source, and makes it more subservient to his use or fancy. He
unconsciously strengthens those variations which he prizes when he plants the
seed of a favorite fruit, preserves a favorite domestic animal, drowns the
uglier kittens of a litter, and allows only the handsomest or the best mousers
to propagate. Still more, by methodical selection, in recent times almost
marvelous results have been produced in new breeds of cattle, sheep, and
poultry, and new varieties of fruit of greater and greater size or excellence.

It is said that all domestic varieties, if left to run wild, would
revert to their aboriginal stocks. Probably they would wherever various races of
one species were left to commingle. At least the abnormal or exaggerated
characteristics induced by high feeding, or high cultivation and prolonged
close breeding, would promptly disappear; and the surviving stock would soon
blend into a homogeneous result (in a way presently explained), which would
naturally be taken for the original form; but we could seldom know if it were
so. It is by no means certain that the result would be the same if the races
ran wild each in a separate region. Dr. Hooker doubts if there is a true
reversion in the case of plants. Mr. Darwin's observations rather favor it in
the animal kingdom. With mingled races reversion seems well made out in the
case of pigeons. The common opinion upon this subject therefore probably has
some foundation, But even if we regard varieties as oscillations around a
primitive centre or type, still it appears from the readiness with which such
varieties originate that a certain amount of disturbance would carry them
beyond the influence of the primordial attraction, where they may become new
centres of variation.

Some suppose that races cannot be perpetuated indefinitely even by
keeping up the conditions under which they were fixed; but the high antiquity
of several, and the actual fixity of many of them, negative this assumption.
"To assert that we could not breed our cart and race horses, long and
short horned cattle, and poultry of various breeds, for almost an infinite
number of generations, would be opposed to all experience."

Why varieties develop so readily and deviate so widely under
domestication, while they are apparently so rare or so transient in free
Nature, may easily be shown. In Nature, even with hermaphrodite plants, there
is a vast amount of cross-fertilization among various individuals of the same
species. The inevitable result of this (as was long ago explained in this
Journal [I-7]) is to repress variation, to keep the mass of a species
comparatively homogeneous over any area in which it abounds in individuals.
Starting from a suggestion of the late Mr. Knight, now so familiar, that close
interbreeding diminishes vigor and fertility; [I-8] and perceiving that
bisexuality is ever aimed at in Nature -- being attained physiologically in
numerous cases where it is not structurally -- Mr. Darwin has worked out the
subject in detail, and shown how general is the concurrence, either habitual or
occasional, of two hermaphrodite individuals in the reproduction of their kind;
and has drawn the philosophical inference that probably no organic being
self-fertilizes indefinitely; but that a cross with another individual is
occasionally -- perhaps at very long intervals -- indispensable. We refer the
reader to the section on the intercrossing of individuals (pp. 96 -- 101), and
also to an article in the Gardeners' Chronicle a year and a half ago, for the
details of a very interesting contribution to science, irrespective of
theory.In domestication, this
intercrossing may be prevented; and in this prevention lies the art of
producing varieties. But "the art itself is Nature," since the whole
art consists in allowing the most universal of all natural tendencies in
organic things (inheritance) to operate uncontrolled by other and obviously
incidental tendencies. No new power, no artificial force, is brought into play
either by separating the stock of a desirable variety so as to prevent mixture,
or by selecting for breeders those individuals which most largely partake of
the peculiarities for which the breed is valued. {I-9]

We see everywhere around us the remarkable results which Nature may
be said to have brought about under artificial selection and separation. Could
she accomplish similar results when left to herself? Variations might begin, we
know they do begin, in a wild state. But would any of them be preserved and
carried to an equal degree of deviation? Is there anything in Nature which in
the long-run may answer to artificial selection? Mr. Darwin thinks that there
is; and Natural Selection is the key-note of his discourse,

As a preliminary, he has a short chapter to show that there is
variation in Nature, and therefore something for natural selection to act upon.
He readily shows that such mere variations as may be directly referred to
physical conditions (like the depauperation of plants in a sterile soil, or
their dwarfing as they approach an Alpine summit, the thicker fur of an animal
from far northward, etc.), and also those individual differences which we
everywhere recognize but do not pretend to account for, are not separable by
any assignable line from more strongly-marked varieties; likewise that there is
no clear demarkation between the latter and sub-species, or varieties of the
highest grade (distinguished from species not by any known inconstancy, but by
the supposed lower importance of their characteristics); nor between these and
recognized species. "These differences blend into each other in an
insensible series, and the series impresses the mind with an idea of an actual
passage."

This gradation from species downward is well made out. To carry it
one step farther upward, our author presents in a strong light the differences
which prevail among naturalists as to what forms should be admitted to the rank
of species. Some genera (and these in some countries) give rise to far more
discrepancy than others; and it is concluded that the large or dominant genera
are usually the most variable. In a flora so small as the British, 182 plants,
generally reckoned as varieties, have been ranked by some botanists as species.
Selecting the British genera which include the most polymorphous forms, it
appears that Babington's Flora gives them 251 species, Bentham's only 112, a
difference of 139 doubtful forms. These are nearly the extreme views, but they
are the views of two most capable and most experienced judges, in respect to
one of the best-known floras of the world. The fact is suggestive, that the
best-known countries furnish the greatest number of such doubtful cases.
Illustrations of this kind may be multiplied to a great extent. They make it plain
that, whether species in Nature are aboriginal and definite or not, our
practical conclusions about them, as embodied in systematic works, are not
facts but judgments, and largely fallible judgments-

How much of the actual coincidence of authorities is owing to
imperfect or restricted observation, and to one naturalist's adopting the
conclusions of another without independent observation, this is not the place
to consider. It is our impression that species of animals are more definitely
marked than those of plants; this may arise from our somewhat extended
acquaintance with the latter, and our ignorance of the former. But we are
constrained by our experience to admit the strong likelihood, in botany, that
varieties on the one hand, and what are called closely-related species on the
other, do not differ except in degree. Whenever this wider difference
separating the latter can be spanned by intermediate forms, as it sometimes is,
no botanist long resists the inevitable conclusion. Whenever, therefore, this wider
difference can be shown to be compatible with community of origin, and
explained through natural selection or in any other way, we are ready to adopt
the probable conclusion; and we see beforehand how strikingly the actual
geographical association of related species favors the broader view. Whether we
should continue to regard the forms in question as distinct species, depends
upon what meaning we shall finally attach to that term; and that depends upon
how far the doctrine of derivation can be carried back and how well it can be
supported.

In applying his principle of natural selection to the work in hand,
Mr. Darwin assumes, as we have seen: i. Some variability of animals and plants
in nature; 2. The absence of any definite distinction between slight
variations, and varieties of the highest grade; 3. The fact that naturalists do
not practically agree, and do not increasingly tend to agree, as to what forms
are species and what are strong varieties, thus rendering it probable that
there may be no essential and original difference, or no possibility of
ascertaining it, at least in many cases; also, 4. That the most flourishing and
dominant species of the larger genera on an average vary most (a proposition
which can be substantiated only by extensive comparisons, the details of which
are not given); and, 5. That in large genera the species are apt to be closely
but unequally allied together, forming little clusters round certain species --
just such clusters as would be formed if we suppose their members once to have
been satellites or varieties of a central or parent species, but to have
attained at length a wider divergence and a specific character. The fact of
such association is undeniable; and the use which Mr. Darwin makes of it seems
fair and natural.

The gist of Mr. Darwin's work is to show that such varieties are
gradually diverged into species and genera through natural selection; that
natural selection is the inevitable result of the struggle for existence which
all living things are engaged in; and that this struggle is an unavoidable
consequence of several natural causes, but mainly of the high rate at which all
organic beings tend to increase.

Curiously enough, Mr. Darwin's theory is grounded upon the doctrine
of Malthus and the doctrine of Hobbes. The elder DeCandolle had conceived the
idea of the struggle for existence, and, in a passage which would have
delighted the cynical philosopher of Malmesbury, had declared that all Nature
is at war, one organism with another or with external Nature; and Lyell and
Herbert had made considerable use of it.But Hobbes in his theory of society, and Darwin in his theory of natural
history, alone have built their systems upon it. However moralists and
political economists may regard these doctrines in their original application
to human society and the relation of population to subsistence, their thorough
applicability to the great society of the organic world in general is now
undeniable. And to Mr. Darwin belongs the credit of making this extended
application, and of working out the immensely diversified results with rare
sagacity and untiring patience. He has brought to view real causes which have
been largely operative in the establishment of the actual association and
geographical distribution of plants and animals. In this he must be allowed to
have made a very important contribution to an interesting department of
science, even if his theory fails in the endeavor to explain the origin or
diversity of species."Nothing is
easier," says our author, "than to admit in words the truth of the
universal struggle for life, or more difficult -- at least I have found it so
-- than constantly to bear this conclusion in mind. Yet, unless it be
thoroughly ingrained in the mind, I am convinced that the whole economy of
Nature, with every fact on distribution, rarity, abundance, extinction, and
variation, will be dimly seen or quite misunderstood. We behold the face of
Nature bright with gladness, we often see superabundance of food; we do not see,
or we forget, that the birds which are idly singing round us mostly live on
insects or seeds, and are thus constantly destroying life; or we forget how
largely these songsters, or their eggs, or their nestlings, are destroyed by
birds and beasts of prey; we do not always bear in mind that, though food may
be now superabundant, it is not so at all seasons of each recurring year."
-- (p. 62.)

"There is no exception to the rule that every organic being
naturally increases at so high a rate that, if not destroyed, the earth would
soon be covered by the progeny of a single pair. Even slow-breeding man has
doubled in twenty-five years, and at this rate, in a few thousand years, there
would literally not be standing-room for his progeny. Linnaeus has calculated that
if an annual plant produced only two seeds -- and there is no plant so
unproductive as this -- and their seedlings next year produced two, and so on,
then in twenty years there would be a million plants. The elephant is reckoned
to be the slowest breeder of all known animals, and I have taken some pains to
estimate its pro!)able minimum rate of natural increase; it will be under the
mark to assume that it breeds when thirty years old, and goes on breeding till
ninety years old, bringing forth three pairs of young in this interval; if this
be so, at the end of the fifth century there would be alive fifteen million
elephants, descended from the first pair.

"But we have better evidence on this subject than mere
theoretical calculations, namely, the numerous recorded cases of the
astonishingly rapid increase of various animals in a state of nature, when
circumstances have been favorable to them during two or three following
seasons. Still more striking is the evidence from our domestic animals of many
kinds which have run wild in several parts of the world; if the statements of
the rate of increase of slow-breeding cattle and horses in South America, and latterly in Australia,
had not been well authenticated, they would have been quite incredible. So it
is with plants: cases could be given of introduced plants which have become
common throughout whole islands in a period of less than ten years. Several of
the plants now most numerous over the wide plains of La Plata, clothing square
leagues of surface almost to the exclusion of all other plants, have been
introduced from Europe; and there are plants which now range in India, as I
hear from Dr. Falconer, from Cape Comorin to the Himalaya, which have been
imported from America since its discovery. In such cases, and endless instances
could be given, no one supposes that the fertility of these animals or plants
has been suddenly and temporarily increased in any sensible degree. The obvious
explanation is, that the conditions of life have been very favorable, and that
there has consequently been less destruction of the old and young, and that
nearly all the young have been enabled to breed. In such cases the geometrical
ratio of increase, the result of which never fails to be surprising, simply
explains the extraordinarily rapid increase and wide diffusion of naturalized
productions in their new homes." -- (pp. 64, 65.)

"All plants and animals are tending to increase at a
geometrical ratio; all would most rapidly stock any station in which they could
anyhow exist; the increase must be checked by destruction at some period of
life." -- (p. 65.)

The difference between the
most and the least prolific species is of no account:

"The condor lays a
couple of eggs, and the ostrich a score; and yet in the same country the condor
may be the more numerous of the two. The Fulmar petrel lays but one egg, yet it
is believed to be the most numerous bird in the world." -- (p. 68.)

"The amount of food gives the extreme limit to which each
species can increase; but very frequently it is not the obtaining of food, but
the serving as prey to other animals, which determines the average numbers of
species." -- (p. 68.)

"Climate plays an important part in determining the average
numbers of a species, and periodical seasons of extreme cold or drought I
believe to be the most effective of all checks. I estimated that the winter of
1854 -- '55 destroyed four-fifths of the birds in my own grounds; and this is a
tremendous destruction, when we remember that ten per cent, is an
extraordinarily severe mortality from epidemics with man. The action of climate
seems at first sight to be quite independent of the struggle for existence;
but, in so far as climate chiefly acts in reducing food, it brings on the most
severe struggle between the individuals, whether of the same or of distinct
species, which subsist on the same kind of food, Even when climate, for
instance extreme cold, acts directly, it will be the least vigorous, or those
which have got least food through the advancing winter, which will suffer most.
When we travel from south to north, or from a damp region to a dry, we
invariably see some species gradually getting rarer and rarer, and finally
disappearing; and, the change of climate being conspicuous, we are tempted to
attribute the whole effect to its direct action. But this is a very false view;
we forget that each species, even where it most abounds, is constantly
suffering enormous destruction at some period of its life, from enemies or from
competitors for the same place and food; and if these enemies or competitors be
in the least degree favored by any slight change of climate, they will increase
in numbers, and, as each area is already stocked with inhabitants, the other
species will decrease. When we travel southward and see a species decreasing in
numbers, we may feel sure that the cause lies quite as much in other species
being favored as in this one being hurt. So it is when we travel northward, but
in a somewhat lesser degree, for the number of species of all kinds, and
therefore of competitors, decreases northward; hence, in going northward, or in
ascending a mountain, we far oftener meet with stunted forms, due to the
directly injurious action of climate, than we do in proceeding southward or in
descending a mountain. When we reach the arctic regions, or snow-capped
summits, or absolute deserts, the struggle for life is almost exclusively with
the elements.

"That climate acts in main part indirectly by favoring other
species, we may clearly see in the prodigious number of plants in our gardens
which can perfectly well endure our climate, but which never become
naturalized, for they cannot compete with our native plants, nor resist
destruction by our native animals." -- (pp. 68, 69.)

After an instructive instance
in which "cattle absolutely determine the existence of the Scotch
fir," we are referred to cases in which insects determine the existence of
cattle:

"Perhaps Paraguay offers
the most curious instance of this; for here neither cattle, nor horses, nor
dogs, have ever run wild, though they swarm southward and northward in a feral
state; and Azara and Rengger have shown that this is caused by the greater
number in Paraguay of a certain fly, which lays its eggs in the navels of these
animals when first born. The increase of these flies, numerous as they are,
must be habitually checked by some means, probably by birds. Hence, if certain
insectivorous birds (whose numbers are probably regulated by hawks or beasts of
prey) were to increase in Paraguay, the flies would decrease -- then cattle and
horses would become feral, and this would certainly greatly alter (as indeed I
have observed in parts of South America) the vegetation; this, again, would
largely affect the insects; and this, as we have just seen in Staffordshire,
the insectivorous birds, and so onward in ever-increasing circles of
complexity. We began this series by insectivorous birds, and we had ended with
them. Not that in Nature the relations can ever be as simple as this. Battle
within battle must ever be recurring with varying success; and yet in the
long-run the forces are so nicely balanced that the face of Nature remains
uniform for long periods of time, though assuredly the merest trifle would
often give the victory to one organic being over another. Nevertheless, so profound
is our ignorance, and so high our presumption, that we marvel when we hear of
the extinction of an organic being; and as we do not see the cause, we invoke
cataclysms to desolate the world, or invent laws on the duration of the forms
of life!" -- (pp. 72, 73.)

"When we look at the plants and bushes clothing an entangled
bank, we arc tempted to attribute their proportional numbers and kinds to what
we call chance. But how false a view is this! Every one has heard that when an
American forest is cut down, a very different vegetation springs up; but it has
been observed that the trees now growing on the ancient Indian mounds, in the Southern United States, display
the same beautiful diversity and proportion of kinds as in the surrounding
virgin forests. What a struggle between the several kinds of trees must here
have gone on during long centuries, each annually scattering its seeds by the
thousand; what war between insect and insect -- between insects, snails, and
other animals, with birds and beasts of prey -- all striving to increase, and
all feeding on each other or on the trees, or their seeds and seedlings, or on
the other plants which first clothed the ground and thus checked the growth of
the trees! Throw up a handful of feathers, and all must fall to the ground
according to definite laws; but how simple is this problem compared to the
action and reaction of the innumerable plants and animals which have
determined, in the course of centuries, the proportional numbers and kinds of
trees now growing on the old Indian ruins!" -- (pp. 74, 75.)

For reasons obvious upon
reflection, the competition is often, if not generally, most severe between
nearly related species when they are in contact, so that one drives the other
before it, as the Hanoverian the old English rat, the small Asiatic cockroach
in Russia, its greater congener, etc. And this, when duly considered, explains
many curious results; such, for instance, as the considerable number of
different genera of plants and animals which are generally found to inhabit any
limited area.

"The truth of the
principle that the greatest amount of life can be supported by great
diversification of structure is seen under many natural circumstances. In an
extremely small area, especially if freely open to immigration, and where the
contest between individual and individual must be severe, we always find great
diversity in its inhabitants. For instance, I found that a piece of turf, three
feet by four in size, which had been exposed for many years to exactly the same
conditions, supported twenty species of plants, and these belonged to eighteen
genera, and to eight orders, which showed how much these plants differed from
each other. So it is with the plants and insects on small and uniform islets;
and so in small ponds of fresh water. Farmers find that they can raise most
food by a rotation of plants belonging to the most different orders; Nature
follows what may be called a simultaneous rotation. Most of the animals and
plants which live close round any small piece of ground could live on it
(supposing it not to be in any way peculiar in its nature), and may be said to
be striving to the utmost to live there; but it is seen that, where they come
into the closest competition with each other, the advantages of diversification
of structure, with the accompanying differences of habit and constitution,
determine that the inhabitants, which thus jostle each other most closely,
shall, as a general rule, belong to what we call different genera and
orders." -- (p. 114.)

The abundance of some forms,
the rarity and final extinction of many others, and the consequent divergence
of character or increase of difference among the surviving representatives, are
other consequences. As favored forms increase, the less favored must diminish
in number, for there is not room for all; and the slightest advantage, at first
probably inappreciable to human observation, must decide which shall prevail
and which must perish, or be driven to another and for it more favorable
locality.

We cannot do justice to the interesting chapter upon natural
selection by separated extracts. The following must serve to show how the
principle is supposed to work:

"If during the long
course of ages, and under varying conditions of life, organic beings vary at
all in the several parts of their organization, and I think this cannot be
disputed; if there be, owing to the high geometrical powers of increase of each
species, at some age, season, or year, a severe struggle for life, and this
certainly cannot be disputed: then, considering the infinite complexity of the
relations of all organic beings to each other and to their conditions of
existence, causing an infinite diversity in structure, constitution, and
habits, to be advantageous to them, I think it would be a most extraordinary
fact if no variation ever had occurred useful to each being's own welfare, in
the same way as so many variations have occurred useful to man. But if
variations useful to any organic being do occur, assuredly individuals thus
characterized will have the best chance of being preserved in the struggle for
life; and from the strong principle of inheritance they will tend to produce
offspring similarly characterized. This principle of preservation I have
called, for the sake of brevity, Natural Selection." -- (pp. 126, 127.)

"In order to make it
clear how, as I believe, natural selection acts, I must beg permission to give
one or two imaginary illustrations. Let us take the case of a wolf, which preys
on various animals, securing some by craft, some by strength, and some by
fleetness; and let us suppose that the fleetest prey, a deer for instance, had
from any change in the country increased in numbers, or that other prey had
decreased in numbers, during that season of the year when the wolf is hardest
pressed for food. I can under such circumstances see no reason to doubt that
the swiftest and slimmest wolves would have the best chance of surviving, and
so be preserved or selected -- provided always that they retained strength to
master their prey at this or at some other period of the year, when they might
be compelled to prey on other animals. I can see no more reason to doubt this
than that man can improve the fleetness of his greyhounds by careful and
methodical selection, or by that unconscious selection which results from each
man trying to keep the best dogs without any thought of modifying the breed.

"Even without any change in the proportional numbers of the
animals on which our wolf preyed, a cub might be born with an innate tendency
to pursue certain kinds of prey. Nor can this be thought very improbable; for
we often observe great differences in the natural tendencies of our domestic
animals: one cat, for instance, taking to catching rats, another mice; one cat,
according to Mr. St. John, bringing home winged game, another hares or rabbits,
and another hunting on marshy ground!, and almost nightly catching woodcocks or
snipes. The tendency to catch rats rather than mice is known to be inherited.
Now, if any slight innate change of habit or of structure benefited an
individual wolf, it would have the best chance of surviving and of leaving
offspring. Some of its young would probably inherit the same habits or
structure, and by the repetition of this process a new variety might be formed which
would either supplant or coexist with the parent-form of wolf. Or, again, the
wolves inhabiting a mountainous district, and those frequenting the lowlands,
would naturally be forced to hunt different prey; and from a continued
preservation of the individuals best fitted for the two sites, two varieties
might slowly be formed. These varieties would cross and blend where they met;
but to this subject of intercrossing we shall soon have to return. I may add
that, according to Mr. Pierce, there are two varieties of the wolf inhabiting
the Catskill Mountains in the United States, one with a light greyhound-like
form, which pursues deer, and the other more bulky, with shorter legs, which
more frequently attacks the shepherd's flock." -- (pp. 90, 91.)

We eke out the illustration
here with a counterpart instance, viz., the remark of Dr. Bachman that
"the deer that reside permanently in the swamps of Carolina are taller and
longer-legged than those in the higher grounds." [I-10]

The limits allotted to this article are nearly reached, yet only
four of the fourteen chapters of the volume have been touched. These, however,
contain the fundamental principles of the theory, and most of those
applications of it which are capable of something like verification, relating as
they do to the phenomena now occurring. Some of our extracts also show how
these principles are thought to have operated through the long lapse of the
ages. The chapters from the sixth to the ninth inclusive are designed to
obviate difficulties and objections, "some of them so grave that to this
day," the author frankly says, he "can never reflect on them without
being staggered." We do not wonder at it. After drawing what comfort he
can from "the imperfection of the geological record" (Chapter IX),
which we suspect is scarcely exaggerated, the author considers the geological
succession of organic beings (Chapter X), to see whether they better accord
with the common view of the immutability of species, or with that of their slow
and gradual modification. Geologists must settle that question. Then follow two
most interesting and able chapters on the geographical distribution of plants
and animals, the summary of which we should be glad to cite; then a fitting
chapter upon classification, morphology, embryology, etc., as viewed in the
light of this theory, closes the argument; the fourteenth chapter being a
recapitulation.

The interest for the general reader heightens as the author advances
on his perilous way and grapples manfully with the most formidable difficulties.

To account, upon these principles, for the gradual elimination and
segregation of nearly allied forms -- such as varieties, sub-species, and
closely-related or representative species -- also in a general way for their
geographical association and present range, is comparatively easy, is
apparently within the bounds of possibility. Could we stop here we should be
fairly contented. But, to complete the system, to carry out the principles to
their ultimate conclusion, and to explain by them many facts in geographical
distribution which would still remain anomalous, Mr. Darwin is equally bound to
account for the formation of genera, families, orders, and even classes, by
natural selection. He does "not doubt that the theory of descent with modification
embraces all the members of the same class," and he concedes that analogy
would press the conclusion still further; while he admits that "the more
distinct the forms are, the more the arguments fall away in force." To
command assent we naturally require decreasing probability to be overbalanced
by an increased weight of evidence. An opponent might plausibly, and perhaps
quite fairly, urge that the links in the chain of argument are weakest just
where the greatest stress falls upon them.

To which Mr. Darwin's answer is, that the best parts of the
testimony have been lost. He is confident that intermediate forms must have
existed; that in the olden times when the genera, the families, and the orders,
diverged from their parent stocks, gradations existed as fine as those which
now connect closely related species with varieties. But they have passed and
left no sign. The geological record, even if all displayed to view, is a book
from which not only many pages, but even whole alternate chapters, have been lost
out, or rather which were never printed from the autographs of Nature. The
record was actually made in fossil lithography only at certain times and under
certain conditions (i.e., at periods of slow subsidence and places of abundant
sediment); and of these records all but the last volume is out of print; and of
its pages only local glimpses have been obtained. Geologists, except Lyell,
will object to this -- some of them moderately, others with vehemence. Mr.
Darwin himself admits, with a candor rarely displayed on such occasions, that
he should have expected more geological evidence of transition than he finds,
and that all the most eminent paleontologists maintain the immutability of
species.

The general fact, however, that the fossil fauna of each period as a
whole is nearly intermediate in character between the preceding and the
succeeding faunas, is much relied on. We are brought one step nearer to the
desired inference by the similar "fact, insisted on by all
paleontologists, that fossils from two consecutive formations are far more
closely related to each other than are the fossils of two remote formations.
Pictet gives a well-known instance -- the general resemblance of the organic
remains from the several stages of the chalk formation, though the species are
distinct at each stage. This fact alone, from its generality, seems to have
shaken Prof. Pictet in his firm belief in the immutability of species" (p.
335). What Mr. Darwin now particularly wants to complete his inferential
evidence is a proof that the same gradation may be traced in later periods, say
in the Tertiary, and between that period and the present; also that the later
gradations are finer, so as to leave it doubtful whether the succession is one
of species -- believed on the one theory to be independent, on the other,
derivative -- or of varieties, which are confessedly derivative. The proof of
the finer gradation appears to be forthcoming. Des Hayes and Lyell have
concluded that many of the middle Tertiary and a large proportion of the later
Tertiary mollusca are specifically identical with living species; and this is
still the almost universally prevalent view. But Mr. Agassiz states that,
"in every instance where he had sufficient materials, he had found that
the species of the two epochs supposed to be identical by Des Hayes and Lyell
were in reality distinct, although closely allied species."[I-11]
Moreover, he is now satisfied, as we understand, that the same gradation is
traceable not merely in each great division of the Tertiary, but in particular
deposits or successive beds, each answering to a great number of years; where
what have passed unquestioned as members of one species, upon closer
examination of numerous specimens exhibit differences which in his opinion
entitle them to be distinguished into two, three, or more species. It is plain,
therefore, that whatever conclusions can be fairly drawn from the present
animal and vegetable kingdoms in favor of a gradation of varieties into
species, or into what may be regarded as such, the same may be extended to the
Tertiary period. In both cases, what some call species others call varieties;
and in the later Tertiary shells this difference in judgment affects almost
half of the species!

We pass to a second difficulty in the way of Mr. Darwin's theory; to
a case where we are perhaps entitled to demand of him evidence of gradation
like that which connects the present with the Tertiary mollusca. Wide, very
wide is the gap, anatomically and physiologically (we do not speak of the
intellectual) between the highest quadrumana and man; and comparatively recent,
if ever, must the line have bifurcated. But where is there the slightest
evidence of a common progenitor? Perhaps Mr. Darwin would reply by another
question: where are the fossil remains of the men who made the flint knives and
arrowheads of the Somme Valley?

We have a third objection, one, fortunately, which has nothing to do
with geology. We can only state it here in brief terms. The chapter on
hybridism is most ingenious, able, and instructive. If sterility of crosses is
a special original arrangement to prevent the confusion of species by mingling,
as is generally assumed, then, since varieties cross readily and their
offspring is fertile inter se, there is a fundamental distinction between
varieties and species. Mr. Darwin therefore labors to show that it is not a
special endowment, but an incidental acquirement. He does show that the
sterility of crosses is of all degrees; upon which we have only to say, Natura
non facit saltum, here any more than elsewhere. But, upon his theory he is
bound to show how sterility might be acquired, through natural selection or
through something else. And the difficulty is, that, whereas individuals of the
very same blood tend to be sterile, and somewhat remoter unions diminish this
tendency, and when they have diverged into two varieties the cross-breeds
between the two are more fertile than either pure stock -- yet when they have
diverged only one degree more the whole tendency is reversed, and the mongrel
is sterile, either absolutely or relatively. He who explains the genesis of
species through purely natural agencies should assign a natural cause for this
remarkable result; and this Mr. Darwin has not done. Whether original or
derived, however, this arrangement to keep apart those forms which have, or
have acquired (as the case may be), a certain moderate amount of difference,
looks to us as much designed for the purpose, as does a rachet to prevent
reverse motion in a wheel. If species have originated by divergence, this keeps
them apart.

Here let us suggest a possibly attainable test of the theory of
derivation, a kind of instance which Mr. Darwin may be fairly asked to produce
-- viz., an instance of two varieties, or what may be assumed as such, which
have diverged enough to reverse the movement, to bring out some sterility in
the crosses. The best marked human races might offer the most likely case. If
mulattoes are sterile or tend to sterility, as some naturalists confidently
assert, they afford Mr. Darwin a case in point. If, as others think, no such
tendency is made out, the required evidence is wanting.

A fourth and the most formidable difficulty is that of the
production and specialization of organs.

It is well said that all organic beings have been formed on two
great laws: unity of type, and adaptation to the conditions of existence.[I-12]
The special teleologists, such as Paley, occupy themselves with the latter
only; they refer particular facts to special design, but leave an overwhelming
array of the widest facts inexplicable. The morphologists build on unity of
type, or that fundamental agreement in the structure of each great class of
beings which is quite independent of their habits or conditions of life; which
requires each individual "to go through a certain formality," and to
accept, at least for a time, certain organs, whether they are of any use to him
or not. Philosophical minds form various conceptions for harmonizing the two views
theoretically. Mr. Darwin harmonizes and explains them naturally. Adaptation to
the conditions of existence is the result of natural selection; unity of type,
of unity of descent. Accordingly, as he puts his theory, he is bound to account
for the origination of new organs, and for their diversity in each great type,
for their specialization, and every adaptation of organ to function and of
structure to condition, through natural agencies. Whenever he attempts this he
reminds us of Lamarck, and shows us how little light the science of a century
devoted to structural investigation has thrown upon the mystery of
organization. Here purely natural explanations fail. The organs being given,
natural selection may account for some improvement; if given of a variety of sorts
or grades, natural selection might determine which should survive and where it
should prevail.

On all this ground the only line for the theory to take is to make
the most of gradation and adherence to type as suggestive of derivation, and
unaccountable upon any other scientific view -- deferring all attempts to
explain how such a metamorphosis was effected, until naturalists have explained
how the tadpole is metamorphosed into a frog, or one sort of polyp into
another. As to why it is so, the philosophy of efficient cause, and even the
whole argument from design, would stand, upon the admission of such a theory of
derivation, precisely where they stand without it. At least there is, or need
be, no ground of difference here between Darwin and Agassiz. The latter will
admit, with Owen and every morphologist, that hopeless is the attempt to
explain the similarity of pattern in members of the same class by utility or
the doctrine of final causes. "On the ordinary view of the independent
creation of each being, we can only say that so it is, that it has so pleased
the Creator to construct each animal and plant." Mr. Darwin, in proposing
a theory which suggests a how that harmonizes these facts into a system, we
trust implies that all was done wisely, in the largest sense designedly, and by
an intelligent first cause. The contemplation of the subject on the
intellectual side, the amplest exposition of the unity of plan in creation,
considered irrespective of natural agencies, leads to no other conclusion.

We are thus, at last, brought to the question, What would happen if
the derivation of species were to be substantiated, either as a true physical
theory, or as a sufficient hypothesis? What would come of it? The inquiry is a
pertinent one, just now. For, of those who agree with us in thinking that
Darwin has not established his theory of derivation many will admit with us
that he has rendered a theory of derivation much less improbable than before;
that such a theory chimes in with the established doctrines of physical
science, and is not unlikely to be largely accepted long before it can be
proved. Moreover, the various notions that prevail -- equally among the most
and the least religious -- as to the relations between natural agencies or
phenomena and efficient cause, are seemingly more crude, obscure, and
discordant, than they need be.

It is not surprising that the doctrine of the book should be
denounced as atheistical. What does surprise and concern us is, that it should
be so denounced by a scientific man, on the broad assumption that a material
connection between the members of a series of organized beings is inconsistent
with the idea of their being intellectually connected with one another through
the Deity, i.e., as products of one mind, as indicating and realizing a
preconceived plan. An assumption the rebound of which is somewhat fearful to
contemplate, but fortunately one which every natural birth protests against.

It would be more correct to say that the theory in itself is
perfectly compatible with an atheistic view of the universe. That is true; but
it is equally true of physical theories generally. Indeed, it is more true of
the theory of gravitation, and of the nebular hypothesis, than of the
hypothesis in question. The latter merely takes up a particular, proximate
cause, or set of such causes, from which, it is argued, the present diversity
of species has or may have contingently resulted. The author does not say
necessarily resulted; that the actual results in mode and measure, and none
other, must have taken place. On the other hand, the theory of gravitation and
its extension in the nebular hypothesis assume a universal and ultimate
physical cause, from which the effects in Nature must necessarily have
resulted. Now, it is not thought, at least at the present day, that the
establishment of the Newtonian theory was a step toward atheism or pantheism.
Yet the great achievement of Newton consisted in proving that certain forces
(blind forces, so far as the theory is concerned), acting upon matter in certain
directions, must necessarily produce planetary orbits of the exact measure and
form in which observation shows them to exist -- a view which is just as
consistent with eternal necessity, either in the atheistic or the pantheistic
form, as it is with theism.

Nor is the theory of derivation particularly exposed to the charge
of the atheism of fortuity; since it undertakes to assign real causes for
harmonious and systematic results. But, of this, a word at the close.

The value of such objections to the theory of derivation may be
tested by one or two analogous cases. The common scientific as well as popular
belief is that of the original, independent creation of oxygen and hydrogen,
iron, gold, and the like. Is the speculative opinion now increasingly held,
that some or all of the supposed elementary bodies are derivative or compound,
developed from some preceding forms of matter, irreligious? Were the old
alchemists atheists as well as dreamers in their attempts to transmute earth
into gold? Or, to take an instance from force (power) -- which stands one step
nearer to efficient cause than form -- was the attempt to prove that heat,
light, electricity, magnetism, and even mechanical power, are variations or
transmutations of one force, atheistical in its tendency? The supposed
establishment of this view is reckoned as one of the greatest scientific
triumphs of this century.

Perhaps, however, the objection is brought, not so much against the
speculation itself, as against the attempt to show how derivation might have
been brought about. Then the same objection applies to a recent ingenious
hypothesis made to account for the genesis of the chemical elements out of the
ethereal medium, and to explain their several atomic weights and some other
characteristics by their successive complexity -- hydrogen consisting of so
many atoms of ethereal substance united in a particular order, and so on. The
speculation interested the philosophers of the British Association, and was
thought innocent, but unsupported by facts. Surely Mr. Darwin's theory is none
the worse, morally, for having some foundation in fact.

In our opinion, then, it is far easier to vindicate a theistic
character for the derivative theory, than to establish the theory itself upon
adequate scientific evidence. Perhaps scarcely any philosophical objection can
be urged against the former to which the nebular hypothesis is not equally
exposed. Yet the nebular hypothesis finds general scientific acceptance, and is
adopted as the basis of an extended and recondite illustration in Mr. Agassiz's
great work.[I-13]

How the author of this book harmonizes his scientific theory with
his philosophy and theology, he has not informed us. Paley in his celebrated
analogy with the watch, insists that if the timepiece were so constructed as to
produce other similar watches, after a manner of generation in animals, the
argument from design would be all the stronger. What is to hinder Mr. Darwin
from giving Paley's argument a further a-fortiori extension to the supposed
case of a watch which sometimes produces better watches, and contrivances
adapted to successive conditions, and so at length turns out a chronometer, a
town clock, or a series of organisms of the same type? From certain incidental
expressions at the close of the volume, taken in connection with the motto
adopted from Whewell, we judge it probable that our author regards the whole
system of Nature as one which had received at its first formation the impress
of the will of its Author, foreseeing the varied yet necessary laws of its
action throughout the whole of its existence, ordaining when and bow each
particular of the stupendous plan should be realized in effect, and -- with Him
to whom to will is to do -- in ordaining doing it, Whether profoundly
philosophical or not, a view maintained by eminent philosophical physicists and
theologians, such as Babbage on the one hand and Jowett on the other, will
hardly be denounced as atheism. Perhaps Mr. Darwin would prefer to express his
idea in a more general way, by adopting the thoughtful words of one of the most
eminent naturalists of this or any age, substituting the word action for
"thought," since it is the former (from which alone the latter can be
inferred) that he has been considering. "Taking Nature as exhibiting thought
for my guide, it appears to me that while human thought is consecutive, Divine
thought is simultaneous, embracing at the same time and forever, in the past,
the present and the future, the most diversified relations among hundreds of
thousands of organized beings, each of which may present complications again,
which to study and understand even imperfectly -- as for instance man himself
--mankind has already spent thousands
of years."[I-14] In thus conceiving of the Divine Power in act as
coetaneous with Divine Thought, and of both as far as may be apart from the
human element of time, our author may regard the intervention of the Creator
either as, humanly speaking, done from all time, or else as doing through all
time. In the ultimate analysis we suppose that every philosophical theist must
adopt one or the other conception.

A perversion of the first view leads toward atheism, the notion of
an eternal sequence of cause and effect, for which there is no first cause -- a
view which few sane persons can long rest in. The danger which may threaten the
second view is pantheism. We feel safe from either error, in our profound
conviction that there is order in the universe; that order presupposes mind;
design, will; and mind or will, personality. Thus guarded, we much prefer the
second of the two conceptions of causation, as the more philosophical as well
as Christian view -- a view which leaves us with the same difficulties and the
same mysteries in Nature as in Providence, and no other. Natural law, upon this view, is the human conception
of continued and orderly Divine action.

We do not suppose that less power, or other power, is required to
sustain the universe and carry on its operations, than to bring it into being.
So, while conceiving no improbability of "interventions of Creative mind
in Nature," if by such is meant the bringing to pass of new and fitting
events at fitting times, we leave it for profounder minds to establish, if they
can, a rational distinction in kind between his working in Nature carrying on
operations, and in initiating those operations.

We wished, under the light of such views, to examine more critically
the doctrine of this book, especially of some questionable parts; for instance,
its explanation of the natural development of organs, and its implication of a
"necessary acquirement of mental power" in the ascending scale of
gradation. But there is room only for the general declaration that we cannot
think the Cosmos a series which began with chaos and ends with mind, or of
which mind is a result: that, if, by the successive origination of species and
organs through natural agencies, the author means a series of events which
succeed each other irrespective of a continued directing intelligence -- events
which mind does not order and shape to destined ends -- then he has not
established that doctrine, nor advanced toward its establishment, but has
accumulated improbabilities beyond all belief. Take the formation and the
origination of the successive degrees of complexity of eyes as a specimen. The
treatment of this subject (pp. i88, 189), upon one interpretation, is open to
all the objections referred to; but, if, on the other hand, we may rightly
compare the eye "to a telescope, perfected by the long-continued efforts
of the highest human intellects," we could carry out the analogy, and draw
satisfactory illustrations and inferences from it. The essential, the directly
intellectual thing is the making of the improvements in the telescope or the
steam-engine. Whether the successive improvements, being small at each step,
and consistent with the general type of the instrument, are applied to some of
the individual machines, or entire new machines are constructed for each, is a
minor matter. Though, if machines could engender, the adaptive method would be
most economical; and economy is said to be a paramount law in Nature. The
origination of the improvements, and the successive adaptations to meet new
conditions or subserve other ends, are what answer to the supernatural, and
therefore remain inexplicable. As to bringing them into use, though wisdom
foresees the result, the circumstances and the natural competition will take
care of that, in the long-run. The old ones will go out of use fast enough,
except where an old and simple machine remains still best adapted to a
particular purpose or condition -- as, for instance, the old Newcomen engine
for pumping out coal-pits. If there's a Divinity that shapes these ends, the
whole is intelligible and reasonable; otherwise, not.

We regret that the necessity of discussing philosophical questions
has prevented a fuller examination of the theory itself, and of the interesting
scientific points which are brought to bear in its favor. One of its neatest
points, certainly a very strong one for the local origination of species, and
their gradual diffusion under natural agencies, we must reserve for some other
convenient opportunity.

The work is a scientific one, rigidly restricted to its direct
object; and by its science it must stand or fall. Its aim is, probably, not to
deny creative intervention in Nature -- for the admission of the independent
origination of certain types does away with all antecedent improbability of as
much intervention as may be required -- but to maintain that Natural Selection,
in explaining the facts, explains also many classes of facts which
thousand-fold repeated independent acts of creation do not explain, but leave
more mysterious than ever. How far the author has succeeded, the scientific
world will in due time be able to pronounce.

As these sheets are passing through the press, a copy of the second
edition has reached us. We notice with pleasure the insertion of an additional
motto on the reverse of the title page, directly claiming the theistic view
which we have vindicated for the doctrine. Indeed, these pertinent words of the
eminently wise Bishop Butler comprise, in their simplest expression, the whole
substance of our later pages:

"The only distinct
meaning of the word 'natural' is stated, fixed, or settled; since what is natural
as much requires and presupposes an intelligent mind to render it so, i.e., to
effect it continually or at stated times, as what is supernatural or miraculous
does to effect it for once."